Epithelial tissues

Compounds in animal diets can exert their effects in the gastrointestinal tract or after absorption through the gut epithelial tissue into the bloodstream, or both. On some occasions the administered compounds may be applied topically (Table 1). 

Decken-. overhead, ceiling, roof covering, -gewebe, n. epithelial tissue, -lampe, /. ceiling lamp, dome lamp, -licht, n. skylight. Strich, m. (Leather) daub. 

The binding specificity of d-[ C]glucose by the taste-papillae membranes, compared to that of control membranes isolated from epithelial tissue, has been confirmed in two studies. One inherent problem in the approach is that the stimuli, primarily carbohydrate sweeteners, are not ideal model compounds to use, as they are not active at low concentrations and do not show sufficiently high binding-constants. The use of other stimulus compounds that are at least several hundred times sweeter than sucrose, such as saccharin, dihydrochalcone sweeteners, dipeptide sweeteners, stevioside, perillartine and other sweet oximes, the 2-substituted 5-nitroanilines, and... 

The weak spots, or Achilles heels, of the body occur where the skin ends and mucous epithelial tissues begin (mouth, anus, eyes, ears, nose and urinogenital tract). These mucous membranes present a much more favourable environment for microbial growth than the skin, in that they are warm, moist and rich in nutrients. Such membranes. 

Most bacterial infections confine themselves to the surface of epithelial tissue (e.g. 

Adenoma A nonmalignant tumor of epithelial tissue characterized by glandular structures. 

Carcinoma A malignant growth that arises from epithelium, found in skin or the lining of body organs. Carcinomas tend to infiltrate into adjacent tissue and spread to distant organs or a cancerous tumor of the epithelial tissue of an organ. 

Kunkel EJ, Kim CH, Lazarus NH, et al. CCR10 expression is a common feature of circulating and mucosal epithelial tissue IgA Ab-secreting cells. J Clin Invest 2003 111 1001-1010. 

Ion-dependent solute transport processes such as Na+-glucose and Na+-amino acid cotransporters can be identified in epithelial tissues by observing an elevation in /sc following solute addition in Na+-containing but not Na+-free... 

There is growing evidence implicating Na+-dependent solute transporters and intracellular as well as extracellular Ca2+ in the physiological regulation of the paracellular pathway [81,203,204], Such modulation of paracellular permeability is especially important for drugs such as peptides and oligonucleotides that exhibit poor permeability characteristics across both the cornea and the conjunctiva [150,152,154,155], In addition, ion transporters such as Cl and Ca2+ channels have been implicated in macromolecular transport (see Sections IV.B.2 and IV.B.4). In the following discussion, some key ion transport processes and their possible roles in solute transport across epithelial tissues are summarized. 

Recent work in our laboratory (Kompella, Mathias, and Lee, unpublished observation) has revealed that activation of the cAMP-regulated Cl channels in the conjunctiva also enhances the transcytosis of horseradish peroxidase. 8-Bromo-cAMP (a membrane-permeable analog of cAMP) and terbutaline (a p2-adrenergic agonist known to increase intracellular levels of cAMP in other epithelial tissues [238]), at 0.5 mM, were found to enhance the transport of 100 pg/ mL HRP from the mucosal side to the serosal side of the pigmented rabbit conjunctiva by a factor of 4 (Fig. 11). 

WS Rehm, RL Shoemaker, SS Sanders, JT Tarvin, JA Wright Jr, EA Friday. (1973). Conductance of epithelial tissues with particular reference to the frog s cornea and gastric mucosa. Exp Eye Res 15 533-552. 

This hypothesis would seem testable in a number of ways, one of which I am working on currently. Basically, since epithelial tissue and muscle fibers are present in Placozoa and in the epithelial component of Cnidaria, the specific proteins of epithelia and muscle should show more similarities to each other than to nerve which is absent in Placozoa and derived from amoeboid cells in Cnidaria. My students and I are attempting to test this hypothesis on a broad scale (not confined to Cnidaria) by looking at similarities among tissue-specific proteins in general. The question is Do sequences in proteins identified with epithelia and muscle show more similarities with each other than they do with sequences of specific proteins for other tissues . 

Fig. 18.4. Regional permeability from isolated rat gastrointestinal epithelial tissue as a function of log D for a small database of drug molecules. This figure is a replot of data from...

Damage to the skeleton, hematopoietic tissue of the bone marrow, and epithelial tissues closely apposed to the skeleton has been noted in animals administered 144Ce in relatively soluble forms by inhalation or injection. At relatively early times after exposure the major target organ has been the bone marrow while at later times all three tissues have shown effects of the radiation damage from the l44Ce deposited in the skeleton. 

These cues are important in rearing, territorial, courtship and, in particular, sexual behaviors. The vomeronasal organ (VNO) is separate from the main epithelium in mammals, comprising a thin epithelial tissue within a bony capsule in the lateral wall of the nasal cavity. It is probably vestigial in humans. The VNO epithelium contains at least two populations of microvillar chemosensory neurons one is in the more apical aspects of the epithelium, while the other lies in the more basal region. These two populations of vomeronasal neurons (VNs) are defined by the differential expression of several genes. For example, the apical VNs express the G-protein subunit Ga, while the basal neurons express Ga0. Apical and basal VNs also... 

Symporters are membrane-spanning proteins which translocate two or more solutes in the same direction across the cell membrane. In epithelial tissue, such... 

As would be expected of active protein secreting cells, glandular epithelial tissue, the cytokine secreting cells of the immune system and the blood vessel endothelium, have an extensive internal structure consisting of rough endoplasmic reticulum and numerous mitochondria. Peptide hormones, growth factors and cytokines like all proteins are synthesized by DNA transcription and mRNA translation. The primary transcript of the mRNA may code for an inactive prohormone which requires careful proteolysis to produce the active hormone, as for example in the case of insulin. Adrenocorticotropic hormone (ACTH) is particularly interesting in this respect because... 

The vitamin A needs of the body are by no means centered in any one organ or tissue. It is necessary for vision, for tooth and bone development, for maintenance of healthy epithelial tissue in the skin and in many organs, for reproduction, etc. It is to be expected that deficiency would be exhibited in many ways and that in different individuals the symptoms would not be the same. The benefits of vitamin A administration may thus appear very different in different individuals, and this helps to explain why many kinds of benefits (part of which are probably real) have been ascribed (by physicians as well as others) to vitamin A administration. A substance with such diverse functions is bound to show different effects in different individuals, and, of course, for some individuals who have low requirements and get plenty in their food, its administration will appear to be wholly without effect. Otto Bessey, in discussing the problem of nutrition, has used vitamin A as an illustration of how widely different levels are needed to maintain different functions in experi-... 

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